Caching Result Sets in PHP: Implementing the Caching System in PHP 5 - Completing the caching application: assembling the relevant classes
(Page 4 of 5 )
At this point, we’re armed with the knowledge and the classes needed to implement successfully the complete caching system. To begin with, let’s first list the source code for each one of the reviewed classes and then set up an illustrative example. Here is the first required class, “MySQL”, which, as you probably remember, looked like this:
// class MySQL
class MySQL{
private $conId; // connection identifier
private $host; // MySQL host
private $user; // MySQL username
private $password; // MySQL password
private $database; // MySQL database
// constructor
public function __construct($options=array()){
// validate incoming parameters
if(count($options)>0){
foreach($options as
$parameter=>$value){
if(empty($value)){
throw new Exception('Invalid parameter
'.$parameter);
}
$this->{$parameter}=$value;
}
// connect to MySQL
$this->connectDB();
}
else {
throw new Exception('No
connection parameters were provided');
}
}
// connect to MYSQL server and select database
private function connectDB(){
if(!$this->conId=mysql_connect($this-
>host,$this->user,$this->password)){
throw new Exception('Error connecting to the
server');
}
if(!mysql_select_db($this-
>database,$this->conId)){
throw new Exception('Error
selecting database');
}
}
// perform query
public function query($query){
if(!$this->result=mysql_query
($query,$this->conId)){
throw new Exception('Error
performing query '.$query);
}
// return new Result object
return new Result($this,$this->result);
}
}
Then, the next piece of the puzzle, the “Result” class:
//class Result
class Result {
private $mysql; // instance of MySQL object
private $result; // result set
public function __construct(&$mysql,$result){
$this->mysql=&$mysql;
$this->result=$result;
}
// fetch row
public function fetchRow(){
return mysql_fetch_array($this-
>result,MYSQL_ASSOC);
}
// count rows
public function countRows(){
if(!$rows=mysql_num_rows($this->result)){
throw new Exception('Error
counting rows');
}
return $rows;
}
// count affected rows
public function countAffectedRows(){
if(!$rows=mysql_affected_rows($this-
>mysql->conId)){
throw new Exception('Error
counting affected rows');
}
return $rows;
}
// get ID from last inserted row
public function getInsertID(){
if(!$id=mysql_insert_id($this->mysql-
>conId)){
throw new Exception('Error
getting ID');
}
return $id;
}
// seek row
public function seekRow($row=0){
if(!mysql_data_seek($this->result,$row)){
throw new Exception('Error
seeking data');
}
}
}
Next, let’s list the code for the “arrayProcessor” class:
// class arrayProcessor
class arrayProcessor{
private $data; // data array for processing
// constructor
public function __construct($data=array()){
if(!is_array($data)){
throw new
Exception('Invalid data array');
}
$this->data=$data;
}
// get first array element
public function getFirstElement(){
if(!$data=reset($this->data)){
throw new
Exception('Error fetching first array element');
}
return $data;
}
// get current array element
public function getCurrentElement(){
if(!$data=current($this->data)){
return false;
}
return $data;
}
// get last array element
public function getLastElement(){
if(!$data=end($this->data)){
throw new
Exception('Error fetching last array element');
}
return $data;
}
// get previous array element
public function getPreviousElement(){
if(!$data=prev($this->data)){
return false;
}
return $data;
}
// get next array element
public function getNextElement(){
if(!$data=next($this->data)){
return false;
}
return $data;
}
// reverse array elements
function reverseElements($prekeys=true){
if(!$data=array_reverse($this-
>data,$prekeys)){
throw new
Exception('Error reversing array elements');
}
return $data;
}
// sort array elements
public function sortElements(){
if(!sort($this->data)){
throw new
Exception('Error sorting array elements');
}
return $this->data;
}
// get range of array elements
public function getRange($offset,$length){
if(!$data=array_slice($this->data,intval
($offset),intval($length))){
throw new
Exception('Error fetching range of elements');
}
return $data;
}
// get random array element
public function getRandomElement(){
if(!shuffle($this->data)){
throw new
Exception('Error shuffling array elements');
}
return $this->data[0];
}
// search element in array
public function searchElement($keyword){
return array_search($keyword,$this-
>data);
}
// count array elements
public function countElements(){
if(!$data=count($this->data)){
throw new
Exception('Error counting array elements');
}
return $data;
}
}
Finally, the core piece of the caching system, the “Cache” class:
class Cache{
private $mysql; // instance of MySQL object
private $result; // instance of Result object
private $arrproc; // instance of arrayProcessor object
private $expiry; // cache expire time in seconds
private $cacheFile; // cache file
private $data; // result data array
// constructor
public function __construct(&$mysql,$expiry=7200,$cacheFile='default_cache.txt'){
$this->mysql=&$mysql;
$this->expiry=$expiry;
$this->cacheFile=$cacheFile;
$this->data=array();
}
// if cache is valid, perform query against database. Otherwise, get results from cache file
public function query($query){
if(!$this->isValid()){
$this->result=&$this->mysql-
>query($query);
// read data from MySQL
$this->data=$this->write();
}
else {
// read data from cache file
$this->data=$this->read();
}
// create a new instance of
arrayProcessor object
$this->arrproc=new arrayProcessor($this-
>data);
}
// write cache file
private function write(){
if(!$fp=fopen($this->cacheFile,'w')){
throw new Exception('Error
opening cache file');
}
// lock cache file
if(!flock($fp,LOCK_EX)){
throw new Exception('Unable to
lock cache file');
}
// get result array from query result
while($row=$this->result->fetchRow()){
$contents[]=$row;
}
// write serialized data to cache file
if(!fwrite($fp,serialize($contents))){
throw new Exception('Error
writing to cache file');
}
// unlock cache file
flock($fp,LOCK_UN);
fclose($fp);
unset($fp,$row);
// return query result
return $contents;
}
// read cache file
private function read(){
if(!$contents=unserialize
(file_get_contents($this->cacheFile))){
throw new
Exception('Error reading cache file');
}
// return cached data
return $contents;
}
// determine if cached data is valid or not (time
expiry triggered cache)
private function isValid(){
if(file_exists($this->cacheFile)
&&filemtime($this->cacheFile)>(time()-$this->expiry)){
return true;
}
return false;
}
// fetch row
public function fetchRow(){
if(!$row=$this->arrproc-
>getCurrentElement()){
return false;
}
$this->arrproc->getNextElement();
return $row;
}
// fetch all rows
public function fetchAll(){
$this->arrproc->countElements();
return $this->data;
}
// count rows
public function countRows(){
return $this->arrproc->countElements();
}
// fetch range of rows
public function fetchRange($offset,$length){
return $this->arrproc->getRange
($offset,$length);
}
}
Okay, I think that nothing was left out here. Now, we’re ready to set up an example. Thus, join me in the next section, to see how easily the caching system is put to work.
Next: A practical approximation: putting the caching application to work >>
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